Television executives have already figured out they can attract more viewers during the summer by offering new shows rather than a schedule full of repeats.

Now, there appears to be another reason for them to tune into summer: The use of TiVo and similar ad-zapping devices may be lower than the rest of the year.

A new analysis shows that in the 3.3 million homes with TiVo, viewers watched prime-time shows mostly “live” during the summer rather than recording them for later when they can skip the commercials

In the past two weeks, the majority of the 25 top-rated TiVo shows – including ABC’s summer-replacement hit “Dancing with the Stars” – were viewed mostly in real time with only four shows primarily recorded.

The exact opposite was true in May during the regular TV season, when only four of the top shows were watched mostly live, according to an analysis of TiVo figures by media-planning firm MPG.

Even repeated episodes were more likely to be watched live. Reruns of several scripted shows such as CBS’s “CSI” and ABC’s “Lost” were viewed in live mode.

Moreover, reality shows ranging from NBC’s “The Apprentice” to Fox’s “American Idol” were mostly recorded during the regular TV season. Fox is a division of News Corp., which also owns The Post.

TV and ad executives say it would be premature to declare this a seasonal trend, since the TiVo universe is a small fraction of the more than 100 million U.S. homes with TV sets and it’s still early summer.

But several suggested that one explanation may be less competition for viewers during the off season compared to May “sweeps” when the most popular shows often go head-to-head in a fierce battle for ratings.

“What often happens because the environment is so competitive is that key shows are running against each other,” said Bill Carroll, director of programming of Katz Television Group, adding that the solution “more often than not is to record them.”

Another possibility: people adopt a more easy-going attitude during the summer months and that carries over into their TV viewing habits.

“People aren’t planning their viewing,” said Nina Kanter, director of communications analysis at MPG. “When they have the time they can sit down and watch TV and that includes watching reruns live.”

Regardless, it suggests another reason for the networks to push year-round programming. For the season to date, summer viewing has increased nearly 6 percent compared to 2000.

Industry watchers say that was when the networks realized that relatively cheap summer-replacement shows like “Who Wants to Be a Millionaire” and “Survivor” could become big hits, while shows that had struggled to attract audiences during the year could gain momentum in the off season when there was less competition.

The networks used to write off summer, which was bereft of new programming, believing that people were more interested in heading outdoors, going on vacation and firing up the barbecue.

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Heating up

Summertime is no longer downtime for the TV business, as more new shows attract bigger audiences.